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DRV 8834 nfault pin

chiranjeev n
Prodigy 240 points
Other Parts Discussed in Thread: DRV8834

Hi TI,

           I m using DRV8834 IC. my question is what is the output of nfault  pin when Vm=5V and  not  enabling other pin's sleep,enable,config etc..  without connecting to load .      ( my circuit is as per the EVM layout)  

   the nfault pin goes low to high,and vice verse in ms)  but what i understood is the nfault pin should be HIGH when we give power to VM is that right?for above question

 nfault goes LOW due to some  error ... 

Gnd connection and other discrete components are done as referenced for  indexer mode and the IC is not heating as well.

Im stuck with this for long time. please assist me to come out of this issue......

  • 0
    TI__Guru** 114905 points

    Hi Chiranjeev,

    chiranjeev n said:
       the nfault pin goes low to high,and vice verse in ms)  but what i understood is the nfault pin should be HIGH when we give power to VM is that right?for above question

    Are you saying that nFAULT is toggling on and off? Do you have a scope capture of this? 

    Based on your condition, nFAULT should be inactive. This means that nFAULT should rise to the value that the pullup resistor is connected.

    Please confirm the thermal pad is connected. Also, please report the voltage at the other pins. There may be a bad connection or some other reason for this behavior.

    If you have the EVM, it can be used to compare against your board.

  • 0
    TI__Mastermind 20985 points

    chiranjeev, with at least some of our devices it is normal for the fault pin to briefly toggle during power up.  This can be due to undervoltage detection.  As long as fault doesn't stay latched on, there probably is no fault.

    Best regards,
    RE

  • 0 in reply to RE
    Prodigy 240 points

    Thnx Rick & RE !

               The stepper motor is working fine now thnx for your continuous support.... 

     now  i am facing  some below issues

    1) At  start up, the stepper motor is get stuck  when i rotate the shaft externally then it starts  rotating(the recommended  current and voltage is given as per stepper motor datasheet)

    2) the Reverse voltage protection feature is not in DRV8834?  (when i switch off the supply,    the current  from stepper motor flows to the microcontroller making the controller  on and off simultaneously for few seconds then microcontroller goes off. so that it damages the controller ) 

  • 0 in reply to chiranjeev n
    TI__Mastermind 20985 points

    For #1, you might need to program an acceleration profile.  Inherent to stepper operation, you can't instantly change step speed due to the internal momentum of the rotor.

    For #2, you might want to slow down the motor gradually, or add a Transient Suppression Device to clamp the max voltage.  See this blog for helpful info on how motors can increase the supply voltage: http://e2e.ti.com/blogs_/b/motordrivecontrol/archive/2013/12/13/art-of-stopping-the-motor-vm-pumping.aspx

    Best regards,
    RE